The training of subjects for UTIAS research on dynamics of human pilots

THE TRAINING OF SUBJECTS FOR UTlAS RESEARCH ON DYNAMICS OF HUMAN PILOTS

MARCH 1967

TECHNISCHE

HOGESC mOL

DELFT

VUiGTU1GtJ,;U"1 ~

by

B1SUOUIEEK

Rae R. Simpson

2SMEI'!J&i

..

'

MARCH 1967

THE TRAINING OF SUBJECTS FOR UTIAS RESEARCH ON DYNAMICS OF HUMAN PILOTS

by

Rae R. Simpson

ACKNOWLEDGEMENTS

The author wishes to express his appreciation to Dr. G. N. Patterson and the staff at UTIAS for providing the opportunity to do this work.

Special thanks are extended to Professor B. Etkin for his most helpful advice and guidance throughout the project.

Thanks are also due to M. Gordon-Smith and L. D. Reid for their close co-operation in the project and to the volunteer subjects without whose enthusiastic participation, the study would have been impossible.

Financial support for this program has been received from the Defence Research Board and the National Research Council of Canada.

SUMMARY

This report describes the facility and the techniques used for the initial training of subjects for current research on human pilot dynamics at UTIAS. The data on the progress of training are presented and analyzed for each subject, and criteria are introduced for evaluation of the degree of proficiency of the subject. Initial steps to refine the system for future work are also described.

T ABLE OF CONTENTS

1. INTRODUCTION

1. 1 The Compensatory Control Task 2. THE TRAINING FACILITY

2. 1 Cockpit Environment 2. 2 Visual Display

2. 3 Random Input Signal 2. 4 Control System

2. 4. 1 Control Stick

2. 4. 2 Controlled Element Transfer Function 2. 4. 3 Control Sensitivity

2. 5 System Operation

2. 5. 1 Operating and Monitoring Station 2. 5.2 Operating Procedure

2. 5. 3 Performance Measure -Score

3. TRAINING PROGRAM

3. 1 Subjects

3. 2 Training Procedure 3. 3 Training Progress

3. 4 Performance Criteria for Trained Subjects 3. 5 Role of the Author

4. SYSTEM EVALUATION

4. 1 Influence of Input Level 4. 2 Influence of Stick Sensitivity

5. CONCLUSIONS AND RECOMMENDATIONS

5. 1 Input Signals

5. 2 Stick Sensitivity

5. 3 Performance Criteria 5. 4 The Training Procedure

1 1 2 2 3 3 3 4 4 4 4 5 5 5 5 6 6 7 9 9 9 10 11 11 11 11 12

AtrPENDIX 1 - Sign Convention

APPENDIX 2 - Preliminary System Checkout

APPENDIX 3- Acceleration"and Positional Dynamics

TABLES FIGURES

1. INTRODUCTION

Current research in human pilot dynamics at UTIAS required a number of subjects whose response to a compensatory control task was subject to a minimum of variability. This requirement led to the initiation of a training program to familiarize the subjects with their task and allow them to improve their response.

For the study, it was also considered desirabIe to optimize

the man -machine system and use this optimum as an operating point from which to investigate the subjects' response by varying system parameters. This

required continuous evaluation of the system with a view to improving its overall characteristics wherever possible.

Since there was little previous experience in this type of work at UTIAS, this program was of an exploratory nature and had to be approached somewhat on a trial and error basis, first setting up an operating system, training subjects on it, and then exploring the performance of these subjects and examining the effects of changing system parameters on their performance and opinion.

1. 1 The Compensatory Control Task

In the compensatory control task, the pilot was shown the error existing between the desired and actual system outputs, and, by appropriate manipulation of a control, he was to try to minimize this error. In this experiment, the system output was the difference between a random input signal and a response signal from the man-machine system, and represented the aircraft pitch angle. The pilot was shown this signaIon a visual display and was to control it using a joy-stick.

2. THE TRAINING FACILITY

A CF-100 Mk. 4B flight simulator (ref. 1) was used in

conjunction with an Electronic Associated Inc. PACE 221R analog computer to provide the simulation. The CF -100 cockpit was modified by installation of a control system and visual display. Control system characteristics were simulated on the PACE computer completely independently of the CF-lOO's simulation system. Random noise, taped on an Ampex SP-300 tape recorder, was filtered by the computer to provide the random input signal. The computer also provided computation of the rms of the input and error signals and timed the test runs. Figure 1 presents a block diagram covering the operation of the overall system.

2. 1 Cockpit Environment

The purposes of the cockpit environment were to isolate the sub-ject from laboratory activity which might distract him from his task, and to provide a somewhat realistic atmosphere in which to conduct tests. Modifica-tions inside the cockpit were restricted to the installation of the visual display and the stick. The seat was a Martin- Baker ejection seat, which was standard in the CF-100, in which padding replaced the back-pack parachute on the seat and the seat-pack in the pan. A cockpit layout is shown in figure 2.

To isolate the subject from laboratory sounds, jet engine noise, part of the CF-100 facility, was turned on during all tests. To eliminate dis-traction by changes in laboratory lighting or by the casting of shadows on the

"--canopy, the entire cockpit was initially blacked out from external light. How-ever, many subjects complained of eyestrain when only internal lighting was used. Opinion was much more favourable when external light was admitted through the windshield side panels. The light intensity on the instrument panel was sufficient to read all the instruments without use of internal light, but was not bright enough to cause glare. The windshield side panels were carefully shielded from changes in intensity of general laboratory lighting (figure 3). 2. 2 Visual Display

A Dumont Type 333 dual beam oscilloscope with a 4" diameter face was installed in the cockpit directly in front of the pilot and above the

standard CF-100 instrument panel (figs. 4 & 5). The display was similar in concept to a standard artificial horizon in which the aircraft was represented by the reference marks in the centre of the scope face and the horizon was represented by the cathode ray trace. To correct for parallax errors, zero-ing adjustment controls were installed in the cockpit along with brightness and focus controls for the trace and a brightness control for the reference marks.

In this report, the aircraft had a single degree of freedom, namely pitch, which was represented as a vertical displacement of the horizon line, i. e., upward displacement of the horizon was equivalent to downward pitch of the aircraft, and vice-versa, as for a conventional artificial horizon. No bank angle was displayed at any time so that the horizon line always re-mained parallel to the aircraft reference marks. The pitch error e(t) dis-played was the difference between a random input signal i(t) and the man-machine system output signal p(t), where this output signal was the pilot' s control displacement as transformed by the aircraft dynamics.

2. 3 Random Input Signal

A random noise signal, from an Elgenco Inc. Model 501A

Gaussian Noise Generator, was tape-recorded on the Ampex recorder, giving a signal having a power spectrum which was uniform in the range 0 -40 cps over a sufficiently long period of time. A second-order bandpass filter network on

the FACE computer provided a lower cutoff frequency of O. 32, radians/second

and an upper cutoff frequency of O. 5, 1. 0, or 2. radians/second as desired,

all with cutoff slope s of 40 db / decade.

It was found that if three -minute runs were taken over an

arbitrary section of the tape using such low frequencies, there was considerable variation of the RMS level of the input signal. A histogram of input RMS level

for 100 runs of badwidth 0.32-0.5 radians/second is shown in figure 6. This

variation had a considerable effect on the subjects' scores during the learning process so it was necessary to edit the tape and set up discrete runs of fixed

RMS level and zero mean. These runs were editted only for the O. 32 -2.0

radian/ second bandwidth since the lower frequency inputs were used only as

interim steps to the higher frequency level and at the time the editing was complete, there was very little use still being made of the lower frequencies. The average RMS levels of the inputs of different bandwidth are t abulated in table 1.

2. 4 Control System

Pilot control of the aircraft in pitch was effected by means of a control stick which was moved fore and aft for pitch down and pitch up

respectively. The controlled element transfer function was set up on the FACE computer to give the system response to the pilot' s control action.

2. 4. 1 Control Stick

The control stick (fig. 7) was mounted on a pivot on the floor of the aircraft and was restrained to move only fore and aft between the pilot's

legs. A potentiometer at the base of the stick gave an output signal proportional to the stick deflection from the neutral point. The neutral point was set by

rotating the potentiometer until its centre tap (ground) was at the desired

position. Adjustable stops were used to limit stick deflections and to provide fine adjustment in fore and aft travel to equalize pitch up and pitch down control power a vailable.

The stick was free-moving. There were no spring restraints

Inertia forces were minimized by use of extremely light-weight materials in the construction:aluminum tubing for the shaft and balsa wood for the band grip, so that the stick was equivalent to a mass of less than 3 oz. in the hand.

Because removal of the CF-100 stick base and associated

equipment from the cockpit would have been a time -consuming and difficult task, the base for the isotonic stick was attached to a plate in the floor, offset from the centreline, necessitating a somewhat unorthodox shaft shape to position the stick correctly between the legs of the pilot and also to allow it to rotate without

being obstructed by the CF-100 stick base (see

fig.

8). The stop adjustments

were made so that fore and aft travel was not only equal, but also was limited before the stick hit any obstruction. This allowed a stick travel of -:- O. 33 radians from the neutral position. The corresponding travel of the hand grip

was ~ 6. 5 inches at the top, approximating the stick travel in many conventional

aircraft.

2. 4. 2 Controlled Element Transfer Function

The dynamical characteristics of the controlled element, i. e. ,

the aircraft in pitch were simulated on the PACE computer. For the training program described in this report, the dynamics used were velocity dynamics, having transfer func'ti0n.-

KI

s. This system has a pitch rate proportional to the deflection of the stick.

2. 4. 3 Control Sensitivity

The control stick sensitivity (or control :display ratio or stick gain) was set by performing a series of preliminary flights before the training was started. As a result of this preliminary checkout (see Appendix 2), the control sensitivity for the training program was set at 6. 1 inches/ second per radian (inches/ second deflection rate on the scope per radian of stick deflection).

2. 5 System Operation

2. 5. 1 Operating and Monitoring Station

An operating and monitoring station was set up for the experimenter at the CF-100 instructors ' console (fig. 11). The console was modified by

installation of a remote control unit for the PACE computer, which was located in a separate part of the building, and a patch panel from which trunk lines ran to the computer and to the cockpit, carrying the stick and visual display signals. At this station were the tape recorder for the unfiltered random noise signal, an oscilloscope on which the test run could be monitoreet and a voltmeter to read the RMS input and error signals from the computer at the end of each run. Voice

2. 5. 2 Operating Procedure

All simulator runs described in this report were of three -minute duration. Prior to the start of a run, the subject was briefed verbally over the intercom and was given a five-second countdown. At the end of the three minutes,

the computer went into its qutomatic hold mode, freezing the system until it was manually reset. There was not normally any communication with the subject during the run as this was found to have an adverse effect on his performance.

In the initial phases of training, two subjects would alternate for

two or three runs each during a half-hour session so that each could rest while

the other was flying. Later, to simplify scheduling, each subject performed three consecutive runs, remaining in the cockpit for a two-minute rest between each run, with no apparent adverse effect on his performance.

2. 5. 3. Performance Measure -Score

For the purposes of this project, the measure of performance of a subject during any test run was his "score" which was defined:

score

=

~

><

100 1.2..

where

=

mean square error

i. t. :::r mean square input

Low score was an indication of high performance by the subject. The computer

provided the Q-z.. and

zt"

signals by squaring the e (t) and i (t) signals and integrating over the three minute test period.

3 TRAINING PROGRAM 3. 1 Sub je cts

The subjects used in this project were volunteers who were normally enployed in other duties at UTIAS. Pertinent data for each subject is tabulated in table 2. For subjects who wore glasses during simulator runs,

the visual acuity data was taken with the subject wearing his glasses. JS, who was only 5'3" tall, could not reach the full forward stick position with the shoulder harness fastened so she was allowed to fly with only the lap-belt fastened. All subjects, whether naturally right-handed or left-handed, used their right hand on the stick.

3. 2 Training Procedure

An initial series of six runs, with an input bandwidth of O. 32-0. 5 radians / second, was flown byeach subject to let him become familiar with the system before increasing the bandwidth. Before the first flight, the subject was briefed about the operation of the system, his task, and the control

technique. During initial runs, ,the experimenter issued verbal cues to the

subject as necessary until the subject was sufficiently familiar with the system to correct his own mistakes. A common mistake was to move the stick in the wrong direction, but, with familiarity, the pilot made fewer of these mistakes and corrected them faster. Verbal cuing was not used subsequent to the first few runs. Any problem was then discussed af ter the run was finished.

Following the six familiarization runs, the input bandwidth was increased to O. 32 -1. 0 radians / seconde Learning on the part of the subject was essentially a process of learning from experience. The subject could discuss his technique, or any other difficulty he might encounter, with the experimenter af ter the run, and in some cases, this led to a change in his technique and an improvement in his performance.

The number of runs spent at this bandwidth varied from subject to subject. At first, advancement to the O. 32 -2. 0 radian/ second bandwidth was

made when the subject's score remained below '30 with some consistency, but

the first subjects to advance performed sufficiently well that such rigid criteria were not applied in later advancements. Training at the higher level continued until the subject was "trained ".

3. 3 Training Progress

The progress of each subject was monitored by plotting his score

against the run number (see figures 12 -24). The large variations which

existed from run to run made it difficult to interpret these charts visually. In order to simplify the interpretation, a smoothed curve was drawn through

10-run-average points; i. e., any point on the smoothed curve has abcissa and

ordinate values equal to the average of ten consecutive runs. The next point is found by averaging the ten consecutive runs starting with the second of the runs averaged above. This method was first applied to the chart of subject RS

(fig. 21) by taking averages over five points. However, further smoothing was considered desirabIe so that for all subsequent charts, ten-point averages were used.

The significance of the difference between the first calculated mean of ten points of the O. 32 -2. 0 radian/ second input was tested statistically

with a T -test for subjects BM and NU. For BM, these means were different at

•

different) , and for NU, , the ':means w:eredifferent at the O. 01% significance level. Occasional unexplained failures of the scoring system resulted in loss of data on otherwise complete runs. In these cases, no score is shown

for these runs and the point on the smoothed curve was found by taking the average over the nine remaining runs.

The training charts presented in figures 12 -24 exclude four subjects who were associated with the program for a limited time only and who will not be used as subjects for later research. Although the author (subject R) will not be a subject later, his chart is inc1uded for comparison. Many of his runs served as system checkouts and his training was curtailed so that he could proceed to further checkouts. Except for subjects BB, LR, and R, who had participated in the initial system checkout (Appendix 2), none of the subjects had any previous e xperience on the system.

The distribution in results is shown by the histogram in figure 28 for the last ten runs performed byeach subject and appears to approximate a skewed normal distribution . Much of t,he tail at the higher scores was due to two or three subjects who were behind in the training program.

3. 4 Performance Criteria for Trained Subjects

The setting of criteria to define a "trained " subject was difficult because of the problem of compromising between the ideal and the practical. Several criteria on various measures of the subject's performance are described below. Visual interpretation of progress charts could be of some qualitative

value but it did not provide the quantitative basis desirabIe for future work. Quantitative measurements and criteria were needed to describe the overall trend and variability of the pilot's performance.

Initial measures of the overall trend were made by performing a linear regression analysis (least squares fit of a straight line) on the last ten

scores on the progress chart of each subject. However, run-to-run variability of the subjects' performance was so large th at there was too great an uncertainty in the parameters of the regression line. Finally, aregression line was fitted to the last ten points on the smoothed curve and the uncertainty found to be

much smaller. The slope of this regression line was considered a good measure of the subject' s trend.

For an ideal, fully trained subject, this slope would be zero. But practically, training to this level is impossible so t hat it is suggested that a more useful practical criterion is that

(3 ~ O. 7 per run at a 95% confidence level,

i. e. fbi

+

I

c

l<.0.7

where b= slope of the regression line

B= mean slope of population of which b is a sample b±c = 95% con fidence limits on (3

For further information, the reader is referred to any standard text on statistical analysis such as reference 5.

Figure 27 (c) shows the calculated slope b with the confidence interval c superimposed. It can be seen that the calculated slope contributes most to the

I

bi + Ic

I

level and since for many subjects

I

cl,::::

o.

2, then an equivalent criterion to

fbi

+

Icl<:0.7

would be

I

b

I

~ O. 5

To determine the variability in the pilot's "response, the standard deviation..o was calculated from the last ten runs of each subject. To do this, it was assumed that all these points were from a normal distribution. This assumption is good if the subject is sufficiently trained to pass the slope test. If the subject' s mean score was ~, then for an 80% confi dence interval of

f'A-:!

5, it was required that

/.:) ~ . 5 (units:of score)

This is reasonable consistency to expect of a subject, It may be inferred from figure 27 (b) that it w ould be impractical to set a more stringent criterion.

Satisfaction of the above -mentioned criteria only, still leaves open the possibility that a subjeet's performance is on a temporary plateau and will improve again. Figure 27 (a) shows a large number of subjects whose mean scores have attained a level of below 60. Since these subjects have been in training for almost four months, this would be a practical level of

performance to expect of a subject with good certainty that he is not on a plateau, or if he is, it would be an extended one. Hence it is suggested that a third criterion to be met by a trained subject be that

mean score ~ 60

. where the mean score is calculated over the last ten runs made by the subject.

The results of the aforementioned analyses and the results of application of the criteria suggested are shown in figures 27 and table 3.

3.5 Role of the Author

Due to the ex ploratory nature of this program, the author

trained himself so that he could perform checks of the system before subjects performed runs on it, and also so that he would be conversant with the subjects regarding problems t hey might be having. For example, the author performed feasibility check runs on all input signal bandwidths before the subjects were trained on them. Initial checks were also made on systems where the controlled

element had different dynamical characteristics.

As subjects became more familiar with the concepts of the system ,

such checkouts by the author could be replaced by tests by different subjects which would be statistically more valid. However, the author continued self-training in order to maintain his capability to perform initial exploratory checkouts and to remain conversant with the subjects.

4 SYSTEM EVALUATION

It was desired to optimize the man-machine system to provide an operating point for the research and to train subjects on that system. The

initial step was to train subjects on an interim system as described already and ~ then use them to evaluate the effects of changing the input level and stick

sensitivity in order to optimize the system. Subjects BM, R, LR, and RS were used initially for this evaluation as soon as they could be considered adequately trained. Although they did not all necessarily conform to the criteria stated for a trained subject, their performance was considered adequate to provide useful initial qualitative data on which to base system improvements.

4. 1 Influence of Input Level

The author (R) and subject BM performed the compensatory task using the same stick sensitivity as for training (6. 1

in/

sec per radian)

for five input levels between O. 2 and O. 5 inches RMS. A randomized five-by-five Latin square design':< (ref. 5) was used for the experiment. The results obtained are shown in figure 25 as plots of score and RMS error against RMS input.

':< A Latin square design is a statistical means of setting up the experiment so that five runs were performed on each of five input levels in such a way as to reduce the influence of other factors on the results.

Over the input range tested, the input level had very little effect

on the score. BM showed slight improvement at the higher levels while R's

performance was constant except for the very lowest input .level where it was poorer. This poorer performance at low input levels is predicted by the

threshold describing function found in Goodyear studies (ref 2).

Subject opinion of the low level input reflected the existence of a threshold and the higher degree of precision required to obtain as good a score

as would be obtained using higher inputs. At high input levels, the subjects complained th at the stick sensitivity was inadequate to cope with the large deflection rates sometimes encountered. This inadequancy was not evident

from the scores obtained. It is noteworthy that the comment was that the stick sensitivity was inadequate, not that the input was too high.

4. 2 Influence of Stick Sensitivity

Subjects LR and RS performed tests on five different stick sensitivities using an input level of O. 37 inches RMS. As for the tests of the

input level effects, this experiment was based on a randomized five-by-five

Latin square. The results are shown in figure 26.

Although figure 26 indicates poorer performence at the higher stick sensitivities, both subjects reported increasing preference for increasing gain, actually giving the lowest rating to the lowest gain, which was the one on which they had previously been trained. Reference 3 reports that there. exists a range over which a trained pilot win alter his describing function gain to

maintain a constant overall system gain so that the change in s tiek gain would

not alter the pilot's score . .. Pilot opinion. however, is sensitive to any change

in stick gain so that although the score obtained may not reflect a change, the

pilot' s opinion wilI. At the higher gains in this experiment, the subjects showed a learning trend over the five runs performed at each gain so that it was felt that the poorer average performance was due to the lack of training at these levels.

Work done by Gibbs (ref. 4) for the pilot response to essentially a step input indicated that for velocity control, the optimum control:display

ratio was 1. 32 radians/ second per radian (radians/ second angular velocity of motion of the horizon subtended at the eye per radian movement of the arm).

For the system described in this report, one radian of arm movement corresponded to one -half radian of stick deflection and the distance from the eye to the

oscilloscope display was 28 inches. Hence, for the training program, the control-display ratio was O. 11 radians / second per radian. Exploratory te sts of higher gain than was tested above indicated that subjects did not like gains as high as Gibbs' optimum. This is not to say, however, that the opinion would

'

.

Because of the limited training of subjects prior to tests described here, the data was intended mainly to serve as a qualitative guide to future

training of the subjects. Evaluation of stick gain will continue as training of

subjects on more sensitive sticks is done.

5. CONCLUSION AND RECOMMENDATIONS 5. 1 Input Signals

Completely random inputs from a Gaussian noise generator gave so much variation that it was responsible for part of the variation in the score s obtained by untrained subjects. The use of discrete, edited, but unfiltered runs recorded on tape eliminated most of this variation. It is recommended that discrete filtered runs be recorded on tape since this would free several amplifiers on the analog computer.

For the trained subject, input level changes had little effect on the subject's score. For future work, it would be most practical to select an input level which has been used by previous researchers so that correlation of results would be simplified.

5. 2 Stick Sensitivity

Although in the initial checkout of the system subjects preferred a stick sensitivity of 6. 1 in. / sec. per radian, as they became more proficient on the system, their preference swung to higher sensitivities. The test performed on the influence of stick sensitivities was of qualitative value, but training

will be required at the higher gains before it will be possible to find an optimum sensitivity, and this optimum will be largely determined by pilot opinion.

5. 3 Performance Criteria

The performance criteria set down in section 3. 4 are useful guides to the degree of proficiency attained by a subject on the present system, baf3ed on observed characteristics of subjects who have been trained as described in. this report. These criteria are:

(a) mean score ~ 60 on ten most recent runs

(b) standard deviation of score ~ 5 on ten most recent runs (c) absolute trend in performance ~ O. 7 per run at 95%

confidence level based on last ten points on the smoothed curve.

These criteria are of an arbitrary nature and are valid for the system and task described in this report. Their validity should be re-examined in the light of the quality of data obtained in future research on these subjects.

Since the object of the training program is to produce, for research. investigations,subjects with constant parameters in their describing function, it is recommended that when recording and computational equipment becomes available, an examination be made of the relationship between the variability (i. e., standard deviation) of the data points on the progress chart and the variability of the parameters of the describing function, making possible more conclusive identification of adequately trained subjects by criteria such as those above rather than by means of a costly detailed analysis of the

describing function.

5. 4 The Training Procedure

The present training procedure was to progress through a

succession of input bandwidths to the desired level and through a succession of stick sensitivities to the optimum gain, when this is found. The technique was dictated by the experimenter' s uncertainty about the subjects' ultimate

capabilities. Indications are that there was unnecessary time spent in progressing in this technique.

An alternate technique would be to train the subject completely on the final system although it is possible that the stick gain of the fin al system is so high that an untrained subject would have extreme difficulty in maintaining control.

It is recommended th at training of future subjects be attempted using eaclJ. of these techniques in order to isolate the problems of each. It

would also be valuable to evaluate a compromise technique in which the subject would progress very rapidly to the final system.

1. 2. ~ 3. 4. 5. Reid, L. D. McRuer, D. T. Krendel, E. S. McRuer, D. T. Graham, D Krendel, E. S. Reisener , W., Jr. Gibbs, C. B. Bennet, C. A. Franklin, N. L. REFERENCES

The De sign of a Facility for the Measurement of Human Pilot Dynamics. UTIAS TN-95, June 1965.

Dynamic Response of Human Operators. WADC TR-56-524, October 1957.

Human Pilot Dynamics in Compensatory System. AFFDL-TR-65-15, July 1965.

The Optimal Gain of Manually Controlled Machines. NRC-EIC Symposium on Automatic Control, June 1961.

Statistical Analysis in Chemistry and the Chemical Industry. Wiley, New York, May 1963.

APPENDIX 1

Sign Convent ion

The sign convention below is consistent with the training system block diagram shown in figure 1 and was used throughout this paper.

i (t): e (t) : o (t): P (t) :

A positive input signal causes a pitch down indication

A positive error signal on the display is a pitch down indication; i. e. , the horizon is def1.ected up.

Positive pilot output is produced in response to a positive error e (t) and is a stick back movement.

-

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--

--

--

---APPENDIX 2

Preliminary System Checkout

In order to set the control sensitivity for the training program, the following checkout was performed. The purpose of the checkout was not to find an optimum man-machine operating point, but rather to find some starting point for the training program.

Before the cockpit was ready for use, the stick was mounted on a support beneath a standard, straight-back, wooden office chair and an

oscilloscope was placed on a stand in front of the chair the same distance

from a pilot sitting in the chair as it would be in the cockpit. Since the rig was for checkout purposes only, no attempt was made to isolate the pilot from

laboratory disturbanced or in any other way provide a realistic environment. The author (subject R) flew several flights in order to find a general area of input level and stick sensitivity for closer examination. The input signal bandwidth tried first was O. 32 - 1. 0 radians / second but since the author was not experienced with the system, he thought it best to reduce this bandwidth to O. 32 -0. 5 radians/ second to provide an easier task. On the basis of subjective opinion, three stick sensitivities, 3.05, 4.57, and 6. 10 inches/ second per radian (inches/ second deflection rate on the display scope per

radian of stick deflection), and a range of input levels, approximately 0.28-0.65 inches RMS deflection, were selected for further testing.

The author and two other subjects, BB and LR, then performed a series of runs using a random selection of combinations of the input level and the stick sensitivity. Pilot opinion of these runs appeared to confirm that the input levels and stick sensitivities were in the right range for training. General comments indicated that the lowest stick sensitivity was inadequate to cope with the higher inputs. The lowest input was criticized gene rally as being too exacting.

Figures 9 and 10 show the results obtained by one subject plotted for each stick sensitivity against run number and against input level. Since the upper cutoff frequency was very low, there was very little learning curve effect apparent in these results. Visual inspection of the graphs shows that there is less scatter in the results obt ained for the highest sensitivity stick. Subject opinion of the low-sensitivity stick is reflected by the greater amount of scatter for that stick. The re sults for tre other subjects showed

similar effe cts.

It was recognized that subjective opinions from untrained

subjects were not reliable measures of the adequacy or inadequacy of a system, but in the absence of any more conclusive means, this was effective in providing

a starting point for training. As a consequence of these tests, the system selected for initial training had a stick sensitivity of 6. 1 inches/ second per radian and input levels which are tabulated in table 1.

APPENDIX 3

Acceleration and Positional Dynamics

The author performed a series of preliminary checkouts using both acceleration and positional dynamics, of which the transfer functions are K/ s 2 and K respectively, in lieu of the velocity dynamics used for the

training program described in this report. The results given below are intended only as qualitative guides to future programs.

Using the positional dynamics, the author had no difficulty controlling the system. The gain was adjusted until it "felt" be st. The resulting gain was such that fuU stick deflection was equal to the maximum instantaneous input signal which would be encountered on the system, i. e., the lowest gain possible. This is equivalent to the optimum gain found by Gibbs for positional systems (ref. 4).

For the acceleration dynamics, the system was much more difficult to control. In itially, for sensitivity higher than about 20 inches/ sec/ sec per radian, the man-machine system was unstable. Using a sensitivity of 19 in/ sec/ sec per radian, the author practiced on the system with zero input, then with an input of O. 32 -1. 0 radians/ second bandwidth. Control response felt sluggish compared with the velocity dynamics, and as experience was

gained on the system, higher sensitivities were feasible. Qualitative indication is th at training of subjects on this system will be a longer procedure than for velocity dynamics and it wiU be necessary to use a succession of stick gains to reach an optimum, if such can be found.

Input Bandwidth (Radians/ sec)

RMS Level (Inches)

TABLE 1

INPUT NOISE LEVELS

0.32-0.5 0.32-1.0

O. 392 0.405

ot

0. 32-2.0 0.32-2-0

TABLE 2

SUBJECT QUALIFICATIONS

- - -

-Hours Pilot Experience

Subject Age Sex Visual Acuity Glasses Single Engine Glider Instruments Link Trainer

(both eyes) Light

201ft. 14in. Aircraft BB 19 F 20/20 14/17.5 No WB>!o!< 30 M 20/20 14/14 No JB 30 M 20/20 14/14 Yes BF 32 M 20/40 14/14 Yes 90 10 DJ 24 M 20/30 14/14 No BM 41 M 20/40 14/21 No 300* 30 35

LR

23 M 20/15 14/14 No 50 DS 24 M 20/20 14/14 No JS 23 F

ZO/20

14/14 Yes RS 28 M 20/15 14/14 No NU 31 M 20/20 14/14 No SW 23 M 20/20 14/21 Yes 10 160 R 21 M 20/10 14/14 No 170 5 20

TABLE 3

PERFORMANCE OF SUBJECTS at time of writing

Subject Regression Line Slope Mean Standard Trained b c

Ibl

+

lel

Score Deviation

BB -0.255 O. 163 0.418 55.2 5.85 Nö WB +0.830 0.144 0.974 70.4 8. 52 No JB +0.099 0.075 0.174 65.8 3.56 No BF -0.259 0.289 O. 548 78.0 10.61 No DJ -0.883 O. 193 1. 076 57. 1 9.28 No BM +0.034 O. 139 O. 173 44. 8 3.23 Yes LR -0. 344 O. 197 0.541 61. 8 4. 32 No DS -0.264 O. 189 0.453 56. 6 7.80 No

JS Insufficient data available No

RS -0.459 O. 196 0.655 54.5 3. 30 Yes

Tape _Random

Recorder noise F i Ite r

InDut sianal l(t)

pu)

disployed

-+

error siQmll Human _{stick movement} Controlled

-e (t) _{Pi lot} om Element KIs

--t el t) SquarinQ ealt)

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2 dt

o-~V

0 Multl pli er

L

Dlvislon t score . [ j2dt

I

by hond

-iU) SquarinQ I1 _(t) .-~

o-~V

Multiplier Figure

31" Adjustable Floor o I 2 3 6

-.,,,.,_ "0

\~

.

Posltlon .. 28 Seat Back 1 ... - - - - 1 3 " - j - - - S " Stick Aft Se at Up \ I"

~

\

-

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1\

I 11" Bearing and Potentiometer Houslng CF-IOO I -.. --Instrument Panel Rudder Bar Extreme Positions

VI

I

I

~

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~---TI-Y---

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1-0 .. - - - - 1 5 " 5 -9 12 I Scale - Inches Figure 2 COCKPIT SCHEMATIC

FiQure

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.

Figure 4

Oscilloscope Irace

7

Positive Error Reference marks Figure 5

VISUAL

DISPLAY

(actua I size)

24 22 20 18

1

_..

16 ₁₄

•

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8

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OK

·30 ·32 ·34 '36 -38 -40 -42 -44 -46 -48 -50

RMS Input Level - Inches •

Figure 6

INPUT LEVEL DISTRIBUTION

for 100 Samples

Figur.

7

Figure 8

20 Kc= 6-10 in/sec/rad 15

f

10

•

...

₅ 0 u fI) 0 0 4 8 12 16 20 24 28 32 36 Run Number

•

20 Kc= 4-57 in/lee/rad 15

J

10

•

...

₅ 0 u fI) 0 0 4 8 12 16 20 24 28 32 36 Run Number

_•

20 Kc= 3-05 in/lee/rad 15

t

10

•

~ 5 u fI) 0 0 4 8 12 16

20

24 28 32 36 Run Number

_•

Figure 9 PRELIMINARY CHECKOUT

Figur.

II

1

o

10 20 30 40 50 60

Run Number

(Subsequent to Preliminory System Checkout)

FiCJure 12

120 110 100 90 80

1

70_•

.,

...

_o u 60 Cl) 50 40 30 20 10 30 Run Number Figure i3 40 50

Training Progress Chart -

Subject WB

120

1

10

o

_{10 20} 30 40 50 60 Run Number Figure 14

1

120 90 80 60

o

,-32--5 rad/sec

o

0-32-1-0 rad/sec 0-32- 2·0 rad/sec I 10 20 30 40 60 Run Number

30 20 10

•

. 0 0 10 20 30 40 50 60 70 Run Number Ffgure 16

1

_.,

~ o CJ Cl) Run Number ..

120 110 100 90 80

1

70 60 Ct

...

0 0 U) 50 40 30 20 10 Run Number ~ (Subeequent to Prelimlnary SYltem Checkout)

Fi;ure 18 .

100

90

.

80

1

70 G)

..

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o

Run Number Figure 19 • Actua I Score oiO-run Average

1

.,

~ o u (/) Run Number Figure 20

r

CD ~ o u en Run Number

f

cv

...

o o Cl) 10 20 30 40 · 50 60 70 ROun Number .. Figure 22

110

100

lro

.

30 40 50 60 10

1

cu

...

o u (/)

o

10 20 30 40 60 10 Run Number

(Sub.equent to Preliminary System Checkout )

Figure 24

L

•

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f

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o

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RMS INPUT LEVEL (Inches)

• SUBJECT- R· o SUBJECT-B.M.

0·1 0·2 0·3

RMS INPUT LEVEL (lnche.)

FIGURE 25 0·4

•

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f

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SUBJECT - R.S .

o

o

2 4 6 8 ~o 12 14 16 18 20 22 24 26 28 '30

STICK SENSITIVITY (inch •• /llcond/radian) •

FIGURE 26

r- <:

STANDARD DEVIATION OF SCORE (last 10 runs) . MEAN SCORE (last 10 runs)

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10 20 30 40 50 60 70 80 . 90 100

SCORE

..

HISTOGRAM OF PERFORMANCE